FBI Director James Comey testifies on Capitol Hill in Washington, Thursday, July 7, 2016, before the House Oversight Committee to explain his agency's recommendation to not prosecute Hillary Clinton, now the Democratic presidential candidate, over her private email setup during her time as secretary of state. (AP Photo/J. Scott Applewhite)

In more than four hours of non-stop testimony Thursday, FBI Director James Comey faced tough questions from angry Republicans who disputed his decision not to recommend criminal charges against Hillary Clinton.

The FBI spent a year investigating Clinton's use of a personal email account on a private server when she was secretary of state, attempting to determine whether criminal mishandling of classified information occurred. Comey was called before the House Committee on Oversight and Government Reform to defend his agency's work.

While Comey firmly stood by the outcome of the investigation, he did reveal new details about Clinton's conduct, some of which will give fresh ammunition to those attempting to keep the presumptive Democratic presidential nominee from winning the White House this fall.

Some highlights:

1) Gross negligence: Much of the questioning focused on a federal statute that makes it a crime to exhibit "gross negligence" in mishandling classified information. Republicans have suggested the details revealed by Comey would justify a prosecution of Clinton under that law.

Comey spent some time attempting to clarify the difference between what he termed "great carelessness" by Clinton and the legal standard for "gross negligence."

However, his broader point was that the gross negligence provision has only been used in one case since the law was passed in 1917. He does not believe a case could be prosecuted for negligence without also establishing criminal intent.

"No reasonable prosecutor would bring the second case in 100 years focused on gross negligence," Comey said.

He also made clear that the lack of criminality does not excuse Clinton's actions.

"I think she was negligent," he said. "That I can establish."

2) Celebrity hunting: Several Republican lawmakers accused Comey of applying a different standard for Clinton than he would to an average person. Comey repeatedly denied that allegation.

Instead, he argued it would be a double standard and "celebrity hunting" to proceed with charging Clinton because of who she is, when he does not believe someone else would be prosecuted under the same set of facts.

"I'm highly confident there would not be criminal prosecution, no matter who it was," he said.

These false statements included claiming that no classified material was sent or received, that no information was marked as classified, that all work-related emails were turned over, and that the server was secure.

Comey was reluctant to address Clinton's public comments, instead attempting to focus only on what she said to investigators in a three-and-a-half-hour interview Saturday.

"We did not find evidence sufficient to establish that she knew she was sending classified information beyond a reasonable doubt," Comey explained.

New information was revealed about the FBI interview as well. Comey did not personally participate in it and it was not recorded. The committee requested a copy of the form agents filled out summarizing the interview.

Although Clinton was not under oath during the interview, Comey emphasized that lying to the FBI would still have been a crime.

4) Referral: Some of those public statements that turned out to be false were made before Congress under oath during Clinton's testimony on the Benghazi attacks in October. Republicans suggested that constituted perjury.

Comey said Clinton's congressional testimony was not part of the FBI's email investigation. Chairman Jason Chaffetz (R-UT) said the committee would send him a referral to open a new investigation into whether Clinton lied under oath.

5) Consequences: House Speaker Paul Ryan (R-WI) formally requested Thursday that Clinton's security clearance be revoked because of the careless handling of classified material that the FBI investigation revealed.

While Comey maintained that nobody else would face criminal prosecution for doing the same things Clinton did, he emphasized in his testimony that there would be consequences if a current government employee did it. This could include termination, administrative sanctions, or losing clearance.

He refused to definitively assess a hypothetical situation where someone like Clinton was seeking security clearance for an FBI job, though.

"It would be a very important consideration in a suitability determination," he said.

6) Petraeus: Critics have questioned Comey's assertion that no prior precedent existed for prosecuting an official for mishandling classified information under this set of facts. One often-cited case was that of General David Petraeus, who knowingly gave classified information to his lover and biographer.

Comey explained Thursday that the cases are not comparable because Petraeus' conduct was clearly intentional and he tried to obstruct justice. Petraeus ultimately pleaded guilty to a misdemeanor in that case.

"You have obstruction of justice, intentional misconduct, and vast quantity of information," Comey said, enthusiastically affirming that he stands by the recommendation to charge Petraeus.

He rejected efforts to equate Clinton's behavior with other specific officials who have been prosecuted as well.

7) Gmail: One aspect of Clinton's actions that Comey said was particularly troubling was that he could not completely exclude the possibility that her email account was hacked. Unlike the State Department or even email providers like Gmail, Clinton's personal system did not have full-time security staff ensuring that its protection was up to date.

One hacker who did not access the server was Guccifer, the Romanian man who hacked Clinton ally Sidney Blumenthal's email account and exposed the existence of Clinton's private email address. Although Guccifer has claimed he breached Clinton's system, Comey said the FBI interviewed him and he admitted that was not true.

Comey hesitated to publicly discuss details of the FBI's interview of Bryan Pagliano, the tech support aide who set up and maintained Clinton's servers, because he was granted immunity to cooperate with investigators.

8) Sophistication: Questioned about whether Clinton should have recognized paragraphs that were marked as classified in some emails, Comey said the former secretary may not have been "sophisticated enough" technically with respect to classified information to understand the markings.

However, he also acknowledged that those emails did not have the proper headings to identify them as classified so it might be reasonable if Clinton did not realize they were classified.

9) Clearance: Clinton and her top aides had security clearance to view the classified material that was improperly being transmitted on the server, but Comey said as many as ten people who did not have clearance had access to the system.

He also noted that Clinton used multiple devices and servers during her tenure as secretary and the decommissioned ones were handled by private individuals who did not have clearance.

Comey suggested that Clinton's attorneys may not have had proper security clearance to view the classified information in her emails when they determined which ones were work-related. Clinton campaign spokesman Brian Fallon disputed that assertion.

10) Clinton Foundation: Unconfirmed media reports had indicated that the FBI investigation spread to look at the activities of the Clinton Foundation as well.

Asked whether the FBI did investigate or was still investigating the foundation, Comey said he could neither confirm nor deny the existence of an investigation.

11) Trump: A few Democratic committee members used their questioning time to criticize presumptive Republican presidential candidate Donald Trump. Trump has claimed the investigation was "rigged" in Clinton's favor and alleged that the Clintons bribed Attorney General Loretta Lynch to get a favorable outcome.

Comey denied that he decided not to recommend charges because Lynch was bribed. He also rejected suspicions raised by Trump and others about his announcement coming on the day that President Obama was campaigning with Clinton.

"The timing was entirely my own," he said. "Nobody knew I was going to do it."

12) "Hamilton": FBI Director James Comey has not seen it, but he would like to.